Ter Stegen said he "hardly studied" Real Sociedad's penalty takers before making two decisive saves in Wednesday's Spanish Supercopa shootout.
Ter Stegen saved two, was close to saving another which hit the post and almost saved another which crept into the corner as Barça booked their place in Sunday's final.
"We hadn't really studied them but we played them in La Liga and we had seen some of their penalties this season, although it's different in the end. I am super happy," Ter Stegen told Movistar.
"It was a shame not to (save Mikel Oyarzabal's penalty in normal time) because the game would have been different, but I am really happy because we made a huge effort and I think we deserved the win.
"The sensations are good but it's not a moment to be super proud of this situation. We have to win these games and I am happy to have been able to help."
Asked to analyse the game, he added: "In the first 25 minutes they pressed strongly. They did well and we struggled. We found more space between the lines later, they struggled and were more tired and the win is deserved in the end.
"Both teams knew that when you score in extra-time it's difficult (for the other team) to come back. That had one more chance than us, but what counts is winning the game."
Real Madrid or Athletic Club await in Sunday's final.
"I don't mind who we face," Ter Stegen said. "Whoever it is will demand the maximum from us. Now we have to recover from these 120 minutes because it's necessary."